There are a wide variety of fasteners available today to suit many different applications. Nut and bolt combinations are very popular because of their relatively high strength and versatility. Other types of structural fasteners include blind fasteners and lock bolts which have formed or swaged-on locking elements.
Regardless of the particular type of fastener, in many applications it is important to know the tension load developed in the fastener upon installation (i.e., the preload), as well as the ultimate tensile strength of the fastener. Current methods for determining the preload and ultimate tensile strength of fasteners, however, can be time-consuming, inaccurate, and potentially damaging to the load measuring device. One known method, for example, involves a two step process. The first step requires installing the fastener in a first load test fixture. The first load test fixture includes a load measuring device (e.g., a relatively small load cell) positioned under the head of the fastener to measure fastener preload. The second step requires removing the fastener from the first test fixture (or, alternatively, using another fastener), and then installing the fastener in a second load test fixture to determine the ultimate tensile strength of the fastener. Although removing the fastener from the first load test fixture is time-consuming, this two-step process is widely used to avoid damaging the load measuring device during the subsequent ultimate tensile test.